Of or relating to a gazette; published in or suitable for a gazette or official journal.
From 'gazette' plus the suffix '-al' (an adjective-forming suffix meaning 'of or relating to'), similar to words like 'personal' (of persons) and 'national' (of nations).
The '-al' suffix is one of the most common ways to turn nouns into adjectives in English—you can add it to almost any noun to make it an adjective, which is why 'gazettal' sounds formal and official.
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